The conventional method for recovering fermentation-derived products, such as proteins and antibiotics, from the complex fermentation broth matrix is a series of clarification steps to remove insoluble material and one or more steps employing liquid chromatography. Liquid chromatogramphy comprises the application of the product holding fluid onto a solid chromatographic matrix under conditions where the fermentation-derived product binds to the chromatographic matrix while the bulk of impurities pass through the chromatographic column. After a washing phase the bound product is eluted from the column.
This method has several drawbacks. First, chromatography is an expensive method for recovery of fermentation derived products. Second, chromatography is not well suited for continuous processes which are often used in the industrial manufacture of fermentation-derived products. Third, chromatographic column operation is not robust towards normal fermentation-derived impurities such as remnant cells and cellular debris, antifoam, host cells proteins and proteases. Often many sequential steps are needed for a chromatographic recovery, including upstream centrifugation and filtration steps and several chromatographic steps each targetting a certain group of impurities.
Microfiltration has also been used for the purification steps following fermentation. Usually the fermentation broth is cooled in order to attenuate the degradation of the product as well as to inhibit contaminating microorganisms. The ensuing microfiltration is then performed at temperatures of 0° C. to 30° C. to have a compromise between product degradation and performance of the microfiltration. One exception is WO01/87468 which discloses a microfilmtration process of a fermentation-derived product comprising adding activated carbon to a solution of the fermentation-derived product prior to or during the microfiltration process at a microfiltration process temperature of from 25° C. to 65° C.
Generally however, it is a teaching within the field of biotechnology that fermentation-derived products such as protein and antibiotics should be kept in solution at as low temperatures as possible in order to prevent microbial, enzymatic or chemical degradation of the product (Biochemical Engineering Fundamentals, J. E. Bailey, D. F. Ollis, McGraw-Hill Inc., 1986 and Physical Chemistry, P. W. Atkins, Oxford Univ. Press, 1986).
Surprisingly, the present inventors have found that a method for the industrial manufacture of fermentation-derived products which utilizes a microfiltration step performed at elevated temperatures, enables continuous manufacturing and better separation of product and impurities while requiring a reduced number of manufacturing steps.